Speed and barometric responsive fuel control for gas turbines



Jan. 1, 191 s. M. UDALE SPEED AND BAROMETRIC RESP ONSIVE FUEL CONTROLFOR GAS TURBINES Flled March 12, 1945 EHNEN WNQR v Patented Jan. 16,1951 UNITED STATES PAT Stanley M. Udale, Detroit, Mich., assignor toGeorge M. Holley and Earl Holley Application March 12, 1945, Serial No.582,266

3 Claims.

The object of this invention is to control the fuel supply of an engineby the density of the air and the speed of the engine. is installed onan airplane engine and if the airplane is dived, the increase in airdensity during the dive causes the engine to overspeed, and it isdesirable therefore to restrict the fuel supply temporarily during theacceleration period and to allow the fuel supply to gradually increaseto the desired amount after the plane has leveled off and the dive isover.

The figure shows diagrammatically the essential elements of myinvention.

In the figure, l is'the fuel entrance, II is the fuel exit to theengine, not shown, I2 is an engine-driven-pump, which delivers eachrevolution an amount determined by the position of the control lever I3,[4 is a lever connected at one end to a liquid pressure responsiveservomotor piston l5 and at the other end to the engine speed responsivepiston l6.

An altitude or barometric element I'I moves the servomotor valve I8. Anengine-driven pump I9 circulates lubricating oil past a temperatureresponsive heating element 20. When viscosity is high and temperaturelow, element 20 operates so that the effect of viscosity is negligiblebecause of the electric heat available when the temperature is low.

The oil under pressure from pump I9 is conveyed through a passage 40 tocylinder 22 above speed responsive piston l6. An opening 23 in piston I6allows oil to flow past a needle 25 in outlet 24. The needle 25 iscontrolled by lever 26, which is moved by the servomotor piston l5. Aninlet 2'! into cylinder 28 above the piston I5 leads from the oilpressure passage 2| into cylinder 28. A passage 29 admits oil underpressure beneath the piston I5 from the passage 2|.

An outlet passage 30 delivers the oil back to the reservoir 42 from thecentral recess portion of the piston I 5 and also delivers the oilflowing past the needle valve 25 from the cylinder 22, which flowsthrough the opening 23 and past the piston IS.

The pressure generated by the pump I9 is determined by thetherestriction 33. The oil under pressure in chamber 22 compresses a spring3|, which supports piston I6. A stop 32 limits the upward travel of thepiston I6.

Operation Assume that the plane driven by the gas turbine is in a dive,then the elements I! will be compressed by the increase in atmosphericpres- If such a device sure. Then the valve I8 will descend, and oilwill escape through 29 from below the piston I5 past the valve I8 andthen through passage 30 back to the reservoir 42. The pressure inchamber 22 therefore falls and the spring 3| raises the piston IE tostop 32. Hence, one end of the lever i4 rises and fuel discharge frompump I2 is decreased. However, simultaneously the piston I5 descends andthe other end of lever I4 descends, which moves the lever I3 down so asto increase the discharge from the pump I2 and thus the effect of thepiston I6 rising is cancelled out so that actually lever I3 does notmore very much during a dive.

When acceleration is over and when equilibrium is reached, the valve I8assumes the neutral position in which it is shown because the piston I5descends as far as the valve I8 descends.

Then the escape of oil through piston I5 ceases. I

The pressure in 22 then increases and the piston I6 leaves the stop 32until the pressure of spring 3I plus pressure below piston I6 equals thepressure above the piston I6. The position of the valve 25 determinesthe pressure below the piston I6. Meanwhile the valve 25 has been openedsomewhat by the descent of the piston I5; hence, the flow throughorifice 23 has increased and the pressure drop through orifice 23 hasincreased so that the piston IB descends. Hence, the effect of speed ismore pronounced at sea level than it is at altitude. Hence, at sea leveland at high speed, the speed effect of pump I9 ass sts the barometricdevice I! in increasing the rate of discharge per revolut on of the pumpl2 to a maximum at maximum speed.

This device is particularly adapted to control the fuel supply to a gasturbine in which the turbine drives the o l pump I9 and the fuel pump I2at speed proportional to the speed of the turbine. Gas turbines areparticularly susceptible to excessive speeds.

At low speeds, the pressure generated by pump I9 is so low because ofthe comparatively large size of the restriction 33 that the spring 3ipresses the piston I6 against the. stop 32; hence, at low speeds thebarometric element I1 is the only control for the lever I3.

The fuel outlet II is shown enter ng the combustion chamber M of a gasturbine 50. The drive shaft 41 of the gas turbine is shown driving abevel gear 43, which drives a gear connected to a shaft 45 which drivesa variable stroke pump 46, of any well known type, in which there may bereciprocating pistons which engage with an inclined plate 48. Theposition of this plate 48 3 may be moved by the pump control lever I3 tovary the pump discharge in a well known manner. A similar gear and shaft44, also driven by the shaft 1, drives the oil pump l9.

What I claim is:

1. In a speed density fuel supply, an engine speed responsive oil pump,a servomotor piston connected to said oil pump, a barometric responsivemeans, a. servomotor valve connected thereto and adapted to control saidservomotor piston, an engine speed responsive piston, a cylindertherefor, a passage leading from said cylinder and connected to saidengine speed responsive oil pump, aspring supporting said speedresponsive piston and opposing the pressure generated by said pump, afuel supply pump of the positive displacement type, a control levertherefor, a link, one end connected to the servomotor piston, the otherend to the other piston,

means connecting said control lever to said link whereby the controllever is moved both by the servomotor piston in response to liquidpressure changes and by the other piston in response to changes inengine speed.

2. A device as set forth in claim 1 in which there is a restrictedopening from one side of the speed responsive piston to the other, tomodify the pressure on the said latter piston, a return passage from thelow pressure side of said latter piston to the inlet side of the speedresponsive 90 oil pump, a second restriction in said passage, a valvecontrolling said second restriction, pressure responsive means connectedto said last named valve, barometric responsive means controlling saidpressure responsive means so that an increase'in altitude closes saidlast named valve.

3. A device as set forth in claim 1 in which there is a restrictedbypass in said cylinder around said speed responsive piston and arestricted outlet from the low pressure side of said cylinder and avalve therein, said last named valve being controlled by said barometricmeans whereby at high altitudes the valve is moved towards the closedposition.

STANLEY M. UDALE.

REFERENCES CITED The following references are of record in the file ofthis patent:

349,209 Great Britain May 28, 1931

